This L65-33F defrost sensor is a critical thermistor-based component that triggers the defrost cycle when the outdoor coil temperature drops to a calibrated 33°F

If your furnace blower continues to run while the burners remain off

or localized air leaks during a combustion analysis

Whether you are performing a propane conversion or replacing a fouled burner orifice

also recognized in the field as the QC-6

Nu-Calgon 4320-W8 Acid Test Kit This L65-33F defrost sensor isThe Nu Calgon 4320 W8 Phase III Acid Test Kit is a critical diagnostic tool for field technicians to quantify acid contamination in HVACR systems. Unlike basic indicators, this kit utilizes phase separation technology to provide a clear, undeniable color change in the acid indicator layer, eliminating guesswork during service calls. As the direct replacement for 064427, it is engineered for universal compatibility with mineral oil, alkylbenzene, and